Vance a Potential Heavy Rain Threat to Mexico

Satellite images show that Tropical Storm Vance has an expanding area of heavy thunderstorms that have improved in organization since Friday. Vance is over warm waters with low wind shear, so intensification into a Category 1 hurricane by Sunday is a good bet, but the storm's heaviest rains will remain well offshore from Mexico through Sunday. Vance will get pulled to the northeast by a trough of low pressure on Monday, but might not make it all the way to Mexico. The 8 am EDT Saturday run of the SHIPS model predicted that wind shear would remain low, 5 - 10 knots, though Monday, then ramp up significantly on Monday night and Tuesday as Vance gets caught up in the trough of low pressure that will sling it towerds Mexico. The higher wind shear will likely be able to tear Vance apart before landfall, making heavy rain the primary threat. In their 11 am EDT Saturday Wind Probability Forecast, NHC gave a 7 - 11% chance that Vance would bring tropical storm-force winds of 39+ mph to Puerto Vallarta and the tip of the Baja Peninsula. The 06Z Saturday run of the GFDL model predicted that Vance's moisture would bring a swath of heavy rains of 4 - 8" from just northwest of Puerto Vallarta into Texas, Tuesday night into Wednesday.


Figure 1. VIIRS satellite image of Tropical Storm Vance off the Pacific coast of Mexico on Thursday, October 31, 2014. At the time, Vance had top sustained winds of 40 mph. Image credit: NOAA Visualization Lab.

Tropical Storm Nuri may brush Japan
In the Western Pacific, Tropical Storm Nuri is near typhoon strength, and is headed towards Japan. Nuri may pass close enough to Japan on Thursday to bring them heavy rain, but a direct hit appears unlikely.

Quiet in the Atlantic
The Atlantic is quiet today, with no areas of concern to discuss. None of the three reliable models for predicting tropical cyclone genesis predicts any development in the Atlantic over the next five days. With November at hand and El Niño-like atmospheric conditions in place, the odds of getting Tropical Storm Isaias before the end of the Atlantic hurricane season on November 30 are probably around 30%.

Jeff Masters